Lubricated traction gears require special power transmission fluids which transmit the torque of the driving part to the driven part by means of friction. The lubricating film in the contact zone between the two roller members is subjected to shearing by the transmitted frictional forces.
The profile of requirements for traction fluids comprises, inter alia,
good low-temperature flow behavior and sufficient viscosity at operation temperature
sufficiently high coefficient of friction over the operation temperature range
low evaporation losses.
EP-A-082 967 describes organic compounds for use as fluid for the transmission of frictional forces. DE-A-3 321 773 and DE-A-3 337 503 describe cyclic hydrocarbons for use as fluid for traction drive means. DE 1 644 926 describes condensed saturated hydrocarbons as traction fluid. Furthermore, EP-A-319 580 mentions hydrocarbon diesters for use as traction fluids. DE-A-3 327 014 describes terpene ethers.
DE-A-3 327 014 describes, inter alia, Example 6 (here, referred to below as Comparative Example 1). 
Comparative Example 1 tends to crystallize on prolonged standing, has a melting point of from 72 to 75xc2x0 C. and thus does not meet the requirements for good low-temperature behavior. For use as traction fluid, the solidification points must be substantially below xe2x88x9220xc2x0 C.
It was thus the object of the present invention to provide novel compounds having improved low-temperature behavior.
Surprisingly, it was found that certain terpene ethers, in spite of higher molecular weights, nevertheless have substantially lower solidification points and thus meet the criterion of low-temperature flowability.
The invention relates to novel terpene ethers, a process for their preparation and their use, inter alia, as traction fluids or in the area of fragrances and solvents.
The invention thus relates to novel terpene ethers of the general formula I 
in which
m is a number from 2 to 5,
A is a branched or straight-chain alkylene group having 2 to 5 carbon atoms,
R is hydrogen,
C8-C4-alkyl, which is optionally substituted by C5-C12-cycloalkyl, by C7-C12-bicycloalkyl or by C8-C11-tricycloalkyl, it being possible for the cycloalkyl radical or the tricycloalkyl radical to carry a substituent xe2x80x94CH2xe2x80x94Oxe2x80x94R1, or it being possible for the cycloalkyl radical to be substituted by a radical xe2x80x94Oxe2x80x94R1,
C5-C12-cycloalkyl, which may be substituted by a radical xe2x80x94Oxe2x80x94R1,
C7-C12-bicycloalkyl, or
C8-C12-tricycloalkyl,
R1 being hydrogen,
C1-C18-alkyl,
C5-C12-cycloalkyl,
C7-C12-bicycloalkyl, or
cycloalkyl-, bicycloalkyl- or tricycloalkyl-substituted C1-C6-alkyl.
It has also surprisingly been found that these novel terpene ethers have at least an equally high coefficient of friction as, in some cases even a higher coefficient of friction than, Comparative Example 1. This contradicts all expectations based on systematic friction measurements using model substances (literature: Dokumentation des BMFT: Tribologie [BMFT Documentation: Tribology] Vol. 2, published by Springer Verlag Berlin, Heidelberg, N.Y., 1982, pages 281-313). According to this, a decrease in the coefficient of friction under elastohydrodynamic operating conditions would be expected with increasing chain length of the ether bridge between the isobomyl radicals, owing to the associated decrease in the steric hindrance.
Compounds of the formula (I) in which A is a straight-chain or branched alkylene chain having 2-5 carbon atoms, m is 2 or 3 and R has the meaning of one of the radicals mentioned below: hydrogen, alkyl having 3-5 carbon atoms, cycloalkyl having 5-12 carbon atoms, bicycloalkyl having 7-12 carbon atoms and tricycloalkyl having 8-12 carbon atoms are preferred.
Compounds of the formula (I) in which m is 2 or 3 and R is hydrogen or C7-C12-bicycloalkyl are very particularly preferred.
In the terpene ethers according to the inventionxe2x80x94according to IUPAC nomenclature 1,7,7-trimethylbicyclo[2.2.1]hept-2-yl ethers (=isobomyl ethers) the 1,7,7-trimethylbicyclo[2.2.1]hept-2-yl radical may be in the d or I form, preferably in the form of the racemate and the radical 
in the exo and/or endo form.
The novel compounds can be prepared by methods known per se.
The preferred procedure for the preparation of the novel ethers starts from camphene, which is reacted with the alcohols of the general formula 
in which R has the abovementioned meaning. In the reaction taking place in the presence of acidic catalysts according to the equation: 
the camphene undergoes an intermediate Wagner-Meerwein rearrangement reaction to give a camphene intermediate.
The synthesis is carried out at temperatures between room temperature (20xc2x0 C.) and 160xc2x0 C., preferably at from 50 to 140xc2x0 C. and in particular at from 70 to 120xc2x0 C. Depending on the desired product, the reactants can be used in equimolar amounts or an excess of one or other reactant can be employed. An excess of camphene proved advantageous for the synthesis of diisobornyl ethers.
Catalysts used are mineral acids, such as sulfuric acid, perchloric acid, phosphoric acid, chlorosulfonic acid, etc., strong organic acids, such as p-toluenesulfonic acid, methanesulfonic acid and camphor-10-sulfonic acid, acidic ion exchangers or Friedel-Crafts catalysts, such as boron trifluoride and its adducts (e.g. etherates, glacial acetic acid complex), aluminum chloride, zinc chloride, PdCl2, Pd(OAc)2, SbCl3, SbCl5, YtCl3, LaCl3, zeolites and others, in amounts of from 0.1 to 10, preferably from 0.5 to 6 and in particular from 1 to 4, % by weight, based on camphene used.
The reaction can be carried out in the presence or in the absence of inert solvents. Suitable solvents are, for example, aliphatic hydrocarbons such as pentane, hexane, naphtha fractions, chloroform or carbon tetrachloride, aromatic hydrocarbons such as toluene, xylene or chlorobenzene, cycloaliphatic hydrocarbons, such as cyclohexane or cyclooctane, or ethers, such as dioxane, dibutyl ether or ethylene glycol dimethyl ether. The procedure without the addition of solvent is particularly advisable.
In the reaction, in general, all reactants can be initially introduced in their total amount, including the catalyst. In some cases, the reaction takes place slightly exothermally so that in this case it is advantageous initially to introduce the catalyst and the alcohol and to add the camphene at the desired temperature.
Diethylene glycol, triethylene glycol, dipropylene glycol and tripropylene glycol are particularly preferred as examples of alcohols which are reacted with camphene.
The purification of the reaction products is carried out in general after removal of the catalyst (e.g. washing with water or neutralization by means of bases or simple filtration) by distillation, but for some intended uses a distillation is not necessary. A further possibility for purification is recrystallization from suitable solvents.
The preferred reaction products are low-viscosity to high-viscosity liquids which are colorless to faintly yellow.
As already mentioned, the novel compounds are surprisingly distinguished by the fact that, in comparison with Comparative Example 1 (Example 6 from DE-A-332 701 A 1), they do not solidify down to xe2x88x9230xc2x0 C. When they are used as traction fluids, the compounds described can be employed alone or as mixtures with other substances, with the main proportion of these mixtures comprising one or more of the compounds described here.
In the traction fluid, the terpene ether is used in a concentration of at least 5% by weight, preferably in a concentration of from 20 to 95% by weight.
Some of the novel compounds have a pronounced fragrance character and can therefore be used alone as fragrances or in a fragrance combination, i.e. in mixtures with synthetic and natural oils, alcohols, aldehydes, ketones or esters, and they are furthermore suitable for perfuming soaps, detergents, powders, bath oils, hair cosmetics, creams and further known fragrance-containing formulations. Owing to their consistency, a major part of the novel terpene ethers is of interest as fixing agents for fragrances, and the compounds suitable for this purpose are viscous liquids and therefore have the property of greatly reducing the volatility of fragrances. Furthermore, some of the products can be used as solvents, for example for resins and coating materials.
Finally, those members of the novel ethers which have a free hydroxyl group are suitable as reactive intermediates, for example for the synthesis of crop protection agents, pesticides and drugs.